Flux applying method and mounting substrate manufacturing method

Abstract

To reduce defective soldering of an electronic component.SOLUTION: The disclosed flux coating method includes a preparation step of preparing a substrate 1 having a pair of lands 2 on each of which a solder precoat 3 is formed, and a coating step of coating at least the solder precoat 3 with flux F. In the application step, the flux F is applied to the intermediate region MR between the pair of lands 2 and the solder precoat 3 on the substrate 1 so that the flux F is accommodated in a rectangular region RR circumscribing the pair of lands 2 when viewed from the normal direction of the substrate 1. The height position H1 of the vertex of the flux F applied to the intermediate region MR is higher than the height position H2 of the vertex of either of the pair of solder precoats 3.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a flux application method and a mounting substrate manufacturing method. [Background technology]

[0002] Conventionally, a method of applying flux to a solder precoat of a substrate on which the solder precoat is provided has been known (for example, Patent Document 1). Patent Document 1 discloses "a method for manufacturing an electronic component mounting substrate, the method comprising: a step (i) of forming a temporary fixing film so as to cover a plurality of solder precoats formed on a plurality of lands of the substrate and an antioxidant film formed so as to cover each of the plurality of solder precoats; a step (ii) of arranging a plurality of electronic components on the plurality of solder precoats via the antioxidant film and the temporary fixing film; and a step (iii) of soldering the plurality of electronic components to the plurality of lands by melting the plurality of solder precoats, wherein the antioxidant film contains a first thermoplastic resin, the temporary fixing film contains an activator and a second thermoplastic resin, and the softening point of the first thermoplastic resin is equal to or lower than the softening point of the second thermoplastic resin." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 254819 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors encountered a new problem while conducting research aimed at commercializing the technology of Patent Document 1. In particular, in the case of extremely small electronic components (hereinafter also referred to as "miniature components"), if there is a difference in height between multiple solder precoats, the electronic component may not come into contact with the lower solder precoat when soldering is performed, for example, by reflow. If soldering is completed without the electronic component and the solder precoat coming into contact, the connection between the land and the electronic component will not be properly made (hereinafter referred to as "electronic component soldering failure"). In this situation, one of the objectives of the present disclosure is to reduce soldering failures of electronic components. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to a flux application method, the flux application method comprising: a preparation step of preparing a substrate having a pair of lands each having a solder precoat formed thereon; and an application step of applying flux to at least the solder precoat, wherein in the application step, the flux is applied to an intermediate region between the pair of lands of the substrate and the solder precoat so that the flux fits within a rectangular region circumscribing the pair of lands when viewed from a normal direction of the substrate, and a height position of a peak of the flux applied to the intermediate region is higher than a height position of any peak of the pair of solder precoats.

[0006] Another aspect of the present disclosure relates to a mounting substrate manufacturing method, the mounting substrate manufacturing method comprising: a preparation step of preparing a substrate having a pair of lands each having a solder precoat formed thereon; a coating step of applying flux to at least the solder precoat; a mounting step of mounting an electronic component on the solder precoat to which the flux has been applied; and a reflow step of heating the substrate to solder the electronic component to the pair of lands, wherein in the coating step, the flux is applied to an intermediate region between the pair of lands on the substrate and to the solder precoat so that the flux fits within a rectangular region circumscribing the pair of lands when viewed from a normal direction of the substrate, and a height position of an apex of the flux applied to the intermediate region is higher than a height position of any apex of the pair of solder precoats. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to reduce soldering defects in electronic components. [Brief explanation of the drawings]

[0008] [Figure 1] 2 is a flowchart of a mounting substrate manufacturing method according to the first embodiment. [Figure 2] 1A to 1C are diagrams for explaining the steps of the mounting substrate manufacturing method, in which (a) to (c) show the preparation steps, and (d) shows the planarization step. [Figure 3] 1A and 1B are diagrams for explaining the steps of the mounting substrate manufacturing method, in which (a) shows the coating step, (b) shows the mounting step, and (c) to (d) show the reflow steps. [Figure 4] 4A and 4B are diagrams showing a part of a mask used in a coating step of the first embodiment, in which (a) is a plan view and (b) is a cross-sectional view taken along line IV-IV. [Figure 5] 1A and 1B are diagrams showing a part of a substrate to which flux has been applied in the application step of the first embodiment, in which (a) is a plan view and (b) is a cross-sectional view taken along line VV. [Figure 6]10A and 10B are diagrams for explaining the steps when there is a difference in height in the solder precoat, where (a) shows the mounting step, and (b) and (c) show the reflow step. [Figure 7] 7A and 7B are diagrams showing a part of a mask used in a coating step of embodiment 2, in which (a) is a plan view and (b) is a cross-sectional view taken along line VII-VII. [Figure 8] 8A and 8B are diagrams showing a part of a substrate to which flux has been applied in the application step of the second embodiment, in which (a) is a plan view and (b) is a cross-sectional view taken along line VIII-VIII. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiments of the flux application method and the mounting substrate manufacturing method according to the present disclosure are described below using examples. However, the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples, but other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained. Note that the "height direction" referred to in the following description refers to the normal direction of the main surface of the substrate on which the lands are formed. Furthermore, in the following description, "higher" means being farther away from the main surface of the substrate on which the lands are formed in the height direction.

[0010] (Flux application method) The flux application method according to the present disclosure is a method for applying flux to a solder precoat of a substrate having lands on which the solder precoat is formed, and includes a preparation step and an application step.

[0011] In the preparation step, a substrate is prepared having a pair of lands, each of which is coated with a solder precoat. The dimensions of the lands may be, for example, 0.08 mm or more and 0.30 mm or less. The solder precoat may be formed by applying solder paste onto the lands and melting and solidifying it by heating and cooling. The height of the solder precoat may be, for example, 20 μm or more and 30 μm or less.

[0012] In the application process, flux is applied to at least the solder precoat. The method for applying the flux is not particularly limited, and for example, a screen printing method can be used. In the application process, the flux is applied to the intermediate region between the pair of lands on the substrate and the solder precoat so that the flux fits within a rectangular region circumscribing the pair of lands when viewed from the normal direction of the substrate. The height position of the peak of the flux applied to the intermediate region is higher than the height position of either peak of the pair of solder precoats.

[0013] Applying flux in this manner reduces soldering defects of electronic components. Specifically, the central portion of an electronic component mounted on a pair of solder precoats contacts the flux applied in the central region and with the highest peak. When heated in this state, the flux contacting the central portion of the electronic component draws the electronic component toward the board. This attracting force allows the electronic component to contact not only the higher solder precoat but also the lower solder precoat, even if there is a difference in height between the pair of solder precoats. Since soldering proceeds with the electronic component in contact with both of the pair of solder precoats, each land and the electronic component can be soldered satisfactorily. Furthermore, because the flux is applied to fit within a specified rectangular area, unintended contact between adjacent electronic components due to the flux can be prevented, even when multiple electronic components are closely spaced.

[0014] The amount of flux applied to the intermediate region may be greater than the amount of flux applied to the solder precoat. In this case, the greater amount of flux applied to the intermediate region allows the above-mentioned attractive force to act more reliably on the electronic component. Furthermore, a smaller amount of flux applied to the solder precoat can further prevent adjacent electronic components from unintentionally coming into contact. The amount of flux applied to the solder precoat refers to the total amount of flux applied to a pair of solder precoats. Furthermore, when the flux applied to the intermediate region and the flux applied to the solder precoat are connected to each other, the boundary between them is defined as a plane extending perpendicular to the substrate along the edge of the land.

[0015] In the application step, the flux may be applied using a mask having a first opening corresponding to the intermediate region and a pair of second openings corresponding to the solder precoat. In this case, the flux corresponding to the intermediate region and the flux corresponding to the solder precoat are applied independently of each other. The thickness of the mask may be, for example, 15 μm or more and 50 μm or less, or 15 μm or more and 25 μm or less. For example, when the electronic component is a 0201 chip, the opening area of ​​the first opening is 2500 μm. 2 More than 10000μm 2 The opening area of ​​each second opening may be, for example, 900 μm or less. 2 Over 4900μm 2 For example, if the electronic component is a 0402 chip, the opening area of ​​the first opening may be 6400 μm 2 More than 40000μm 2 The opening area of ​​the second opening may be 2500 μm or less. 2 More than 10000μm 2 Alternatively, in the application step, the flux may be applied to the solder precoat using a mask having openings corresponding to the solder precoat, and then the flux may be applied to the intermediate region using a dispenser.

[0016] The opening area of ​​the first opening may be larger than the opening area of ​​each of the pair of second openings. In this case, the amount of flux applied to the intermediate region can be easily made larger than the amount of flux applied to the solder precoat. If the opening area of ​​the first opening is S, the opening area of ​​each second opening may be, for example, 0.4S or more and 0.7S or less.

[0017] In the application process, the flux may be applied using a mask having openings that correspond to both the intermediate region and the solder precoat. In this case, the flux corresponding to the intermediate region and the flux corresponding to the solder precoat are applied consecutively. The thickness of the mask may be, for example, 15 μm or more and 50 μm or less, or 15 μm or more and 25 μm or less. For example, if the electronic component is a 0201 chip, the opening area of ​​the opening may be 3000 μm. 2 More than 15000μm 2 For example, if the electronic component is a 0402 chip, the opening area of ​​the opening may be 9000 μm 2 More than 50000μm 2 It may be the following:

[0018] (Mounting board manufacturing method) The mounting substrate manufacturing method according to the present disclosure is a method of applying flux to the solder precoat of a substrate having lands on which a solder precoat has been formed, and then mounting and soldering electronic components onto the substrate. The mounting substrate refers to a substrate on which at least one electronic component is mounted. The mounting substrate manufacturing method according to the present disclosure includes a preparation step, an application step, a mounting step, and a reflow step.

[0019] The preparation process and application process are similar to those of the flux application method according to the present disclosure, and therefore will not be described here.

[0020] In the mounting process, electronic components are mounted on the solder precoat to which flux has been applied. During mounting, the flux applied to the intermediate region contacts the intermediate portion of the electronic component. The size of the electronic component may be, for example, 0.4 mm long x 0.2 mm wide, 0.3 mm long x 0.15 mm wide, 0.25 mm long x 125 mm wide, 0.2 mm long x 0.1 mm wide, or 0.1 mm long x 0.5 mm wide. For example, the electronic component may include electronic components specified by JIS (Japanese Industrial Standards), such as 0402, 03015, 0201, and 01005.

[0021] In the reflow process, the electronic component is soldered to a pair of lands by heating the substrate. During this process, the flux in contact with the middle portion of the electronic component attracts the electronic component toward the substrate, maintaining contact with the solder precoat. This results in good soldering. However, as the size of the electronic component decreases, its weight also decreases, making soldering defects due to differences in the height of the solder precoat more likely to occur. This tendency is particularly pronounced with extremely small components such as 0402, 03015, 0201, and 01005. On the other hand, the mounting substrate manufacturing method according to the present disclosure, as described above, can reduce soldering defects due to differences in the height of the solder precoat, making it particularly suitable for use with such extremely small components.

[0022] As described above, according to the present disclosure, by applying a high amount of flux to a predetermined intermediate region and by applying flux so that it fits within a predetermined rectangular region, it is possible to reduce soldering defects in electronic components.

[0023] An example of a flux application method and a mounting substrate manufacturing method according to the present disclosure will be described in detail below with reference to the drawings. The steps described above can be applied to the steps of the example of the flux application method and the mounting substrate manufacturing method described below. The steps of the example of the flux application method and the mounting substrate manufacturing method described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment. Among the steps of the example of the flux application method and the mounting substrate manufacturing method described below, steps that are not essential to the flux application method and the mounting substrate manufacturing method according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0024] First Embodiment A first embodiment of the present disclosure will be described below. As shown in Fig. 1, a method for manufacturing a mounting substrate according to this embodiment includes a preparation step, a planarization step, a coating step, a mounting step, and a reflow step.

[0025] In the preparation process, a substrate 1 is prepared having a pair of lands 2 each having a solder precoat 3 formed thereon. The preparation process includes a substrate preparation step, a solder paste application step, and a heating and cooling step.

[0026] In the substrate preparation step, as shown in Fig. 2(a), a substrate 1 having a pair of lands 2 is prepared. Each land 2 may be formed in a rectangular shape. Note that the substrate 1 may have a number of lands (not shown) in addition to the pair of lands 2 shown in the figure.

[0027] In the solder paste application step, as shown in Fig. 2(b), solder paste P is applied onto each land 2. The application method is not particularly limited, and for example, a screen printing method can be used. The solder paste P may be a resin paste containing solder particles.

[0028] In the heating and cooling steps, the substrate 1 is heated to melt the solder paste P, and then the substrate 1 is cooled to solidify the molten solder paste P. As a result, a pair of solder precoats 3 are formed on the pair of lands 2, as shown in FIG. 2(c). Residues 4 of the flux components contained in the solder paste P are present on the surface of the solder precoats 3. These residues 4 may or may not be removed before the application step.

[0029] 2(d), the top of the solder precoat 3 is flattened. The flattening method is not particularly limited, and for example, the solder precoat 3 may be flattened by rolling a roller (not shown) against the solder precoat 3.

[0030] In the application process, as shown in FIG. 3(a), flux F is applied to at least the solder precoat 3. In the application process, the flux F is applied using a mask 20 shown in FIG. 4, for example, by off-contact screen printing. The mask 20 has a first opening 21 corresponding to the intermediate region MR between a pair of lands 2 on the substrate 1 and a pair of second openings 22 corresponding to the solder precoat 3. The first opening 21 is circular, and the second opening 22 is rectangular. The opening area of ​​the first opening 21 is larger than the opening area of ​​each of the pair of second openings 22. The thickness of the mask 20 is, for example, 15 μm or more and 25 μm or less. The mask 20 is made of, for example, nickel or stainless steel.

[0031] In the application process, as shown in FIGS. 3(a) and 5, flux F is applied to the intermediate region MR and the solder precoat 3 so that the flux F fits within a rectangular region RR (shown by dotted hatching in FIG. 5(a)) that circumscribes the pair of lands 2 when viewed from the normal direction of the substrate 1. This prevents the occurrence of a bridge phenomenon, in which adjacent electronic components 10 on the substrate 1 are attracted to each other by an excess amount of flux F, causing a short circuit. At this time, the height position H1 of the apex of the flux F applied to the intermediate region MR is higher than the height position H2 of the apex of either of the pair of solder precoats 3. Furthermore, the amount of flux F applied to the intermediate region MR is greater than the amount of flux F applied to the solder precoat 3. Note that in FIG. 5(a), the residue 4 covering the solder precoat 3 is not shown, and only its outline is shown by a dashed line.

[0032] The total amount (or volume) of flux F applied in the application step is preferably 0.5V or more and less than 2V, where V is the volume of the space between the intermediate region MR of the substrate 1 and the underside of the electronic component 10 to be mounted in the mounting step. Here, volume V can be determined from the design dimensions of each land 2, each solder precoat 3, and the electronic component 10. A total amount of flux F of 0.5V or more can achieve good connection between the electronic component 10 and the substrate 1. The total amount of flux F applied in the application step refers to the total amount of flux F applied in the area corresponding to a pair of lands 2 (for example, the area shown in FIG. 3).

[0033] In the mounting process, as shown in FIG. 3(b), an electronic component 10 is mounted on a solder precoat 3 to which flux F has been applied. The electronic component 10 may have a pair of terminals 11 and a middle portion 12 sandwiched between the pair of terminals 11. In the mounting process, the bottom surface of the middle portion 12 of the electronic component 10 comes into contact with the top of the flux F applied to the middle region MR of the substrate 1.

[0034] In the reflow process, as shown in Figures 3(c) and 3(d), the electronic component 10 is soldered to a pair of lands 2 by heating the substrate 1. When the substrate 1 is heated, the flux F liquefies, and the liquefied flux F draws the electronic component 10 toward (i.e., downward) the substrate 1. This maintains contact between each terminal 11 of the electronic component 10 and the solder precoat 3, achieving a good solder connection as shown in Figure 3(d).

[0035] 2 and 3 show the state in which an electronic component 10 is soldered to a substrate 1 in which there is no difference in height between a pair of solder precoats 3 formed on a pair of lands 2. However, as shown in FIG. 6, for example, there may be a difference in height between the pair of solder precoats 3. In this case, as shown in FIG. 6(a), the posture of the electronic component 10 is unlikely to follow the difference in height during the mounting process. However, as shown in FIGS. 6(b) and 6(c), during the reflow process, the liquefied flux F pulls the middle portion 12 of the electronic component 10 downward, so that the terminals 11 of the electronic component 10 are soldered in contact with the solder precoats 3. This allows the electronic component 10 to be successfully soldered to the pair of lands 2, even when there is a difference in height between the pair of solder precoats 3.

[0036] Here, we will explain the advantages of the mounting substrate manufacturing method of this embodiment over the technology of Patent Document 1. First, in the technology of Patent Document 1, a large amount of flux is applied to the area where a pair of lands exists, so that the solder precoat is buried over a wider area than the rectangular area RR of this embodiment. This makes it possible to soften the impact when mounting electronic components with a thickly applied flux.

[0037] However, the technology of Patent Document 1 was found to cause poor soldering of electronic components when there is a difference in height between a pair of solder precoats formed on a pair of lands. Specifically, when the flux fluidizes during reflow, the electronic component is subjected to buoyancy from the flux. For relatively large electronic components other than ultra-small components, the component's own weight is greater than the buoyancy, so even if the solder precoat and the electronic component terminals are spaced apart, the electronic component sinks into the flux due to its own weight, causing the terminals to come into contact with the solder precoat. In contrast, ultra-small components, whose own weight is smaller than the buoyancy of the flux, do not sink into the flux even when it fluidizes, and the terminals do not come into contact with the relatively lower solder precoat, resulting in poor soldering of the electronic component.

[0038] Furthermore, it was discovered that the technology of Patent Document 1 is prone to the above-mentioned bridging phenomenon. That is, when a large amount of applied flux becomes fluid during reflow, the fluidized flux pulls the electronic component, causing contact with the adjacent electronic component and resulting in a short circuit. This bridging phenomenon is particularly likely to occur when the electronic component is extremely small.

[0039] In contrast, in the mounting board manufacturing method of this embodiment, in the application step, flux F is applied to the intermediate region MR between the pair of lands 2 and the solder precoat 3 within the rectangular region RR. The height position H1 of the apex of the flux F applied to the intermediate region MR is set higher than the height position H2 of the apex of either of the pair of solder precoats 3. This limits the total amount of flux F, preventing its buoyancy from hindering the sinking of the electronic component 10. Furthermore, by limiting the total amount of flux F, the fluidized flux F can pull the electronic component 10 downward. That is, the fluidized flux F attempts to spread in all directions and also wet and spread on the surface of the electronic component 10. At this time, the flux F attempting to wet and spread in all directions pulls against the flux F attempting to spread in all directions, so that the electronic component 10 in contact with the flux F is pulled toward the substrate 1. As a result, the terminals 11 of the electronic component 10 come into contact with the solder precoat 3, suppressing the occurrence of defective soldering of the electronic component. If the total amount of flux F is large, not only will the flux F not pull against each other, but the large amount of flux F will cause the electronic component 10 to float up.

[0040] Second Embodiment A second embodiment of the present disclosure will be described. The mounting board manufacturing method of this embodiment differs from the first embodiment in the configuration of the mask 20 used in the application step. Specifically, in the application step of this embodiment, as shown in FIGS. 7 and 8, a mask 20 having an opening 23 that commonly corresponds to both the intermediate region MR of the substrate 1 and the solder precoat 3 is used to apply flux F to the intermediate region MR and the solder precoat 3. The opening 23 has a roughly rectangular shape when viewed in the thickness direction of the mask 20. The other configurations are the same as those of the first embodiment.

[0041] <<Notes>> The above description of the embodiments discloses the following techniques. (Technology 1) a preparation step of preparing a substrate having a pair of lands each having a solder precoat formed thereon; a coating step of coating at least the solder precoat with flux; Equipped with In the application step, the flux is applied to an intermediate region between the pair of lands of the substrate and the solder precoat so that the flux fits within a rectangular region circumscribing the pair of lands when viewed from a normal direction of the substrate; A flux application method, wherein the height position of the peak of the flux applied to the intermediate region is higher than the height position of the peak of either of the pair of solder precoats. (Technology 2) The flux application method according to technique 1, wherein the amount of the flux applied to the intermediate region is greater than the amount of the flux applied to the solder precoat. (Technology 3) The flux application method according to Technology 1 or 2, wherein in the application step, the flux is applied using a mask having a first opening corresponding to the intermediate region and a pair of second openings corresponding to the solder precoat. (Technology 4) The flux applying method according to technique 3, wherein an opening area of ​​the first opening is larger than an opening area of ​​each of the pair of second openings. (Technology 5) The flux application method according to Technique 1 or 2, wherein in the application step, the flux is applied using a mask having an opening commonly corresponding to both the intermediate region and the solder precoat. (Technology 6) a preparation step of preparing a substrate having a pair of lands each having a solder precoat formed thereon; a coating step of coating at least the solder precoat with flux; a mounting step of mounting an electronic component on the solder precoat to which the flux has been applied; a reflow process of soldering the electronic component to the pair of lands by heating the substrate; Equipped with In the application step, the flux is applied to an intermediate region between the pair of lands of the substrate and the solder precoat so that the flux fits within a rectangular region circumscribing the pair of lands when viewed from a normal direction of the substrate; a height position of the peak of the flux applied to the intermediate region being higher than a height position of the peak of either of the pair of solder precoats; (Technology 7) The mounting board manufacturing method according to technique 6, wherein the amount of the flux applied to the intermediate region is greater than the amount of the flux applied to the solder precoat. (Technology 8) The mounting substrate manufacturing method according to Technology 6 or 7, wherein in the coating step, the flux is coated using a mask having a first opening corresponding to the intermediate region and a pair of second openings corresponding to the solder precoat. (Technology 9) The mounting substrate manufacturing method according to technique 8, wherein an opening area of ​​the first opening is larger than an opening area of ​​each of the pair of second openings. (Technology 10) 8. The method for manufacturing a mounting board according to claim 6, wherein in the applying step, the flux is applied using a mask having an opening commonly corresponding to both the intermediate region and the solder precoat. [Industrial Applicability]

[0042] The present disclosure can be used in a flux application method and a mounting substrate manufacturing method. [Explanation of symbols]

[0043] 1: Circuit board 2: Land 3: Solder pre-coating 4:Residue 10: Electronic Components 11: Terminal 12: Middle part 20: Mask 21: First opening 22: Second opening 23:Aperture F: Flux H1: Flux height position H2: Height position of solder precoat MR: intermediate area P: Solder paste RR: Rectangular area

Claims

1. a preparation step of preparing a substrate having a pair of lands each having a solder precoat formed thereon; a coating step of coating at least the solder precoat with flux; Equipped with In the application step, the flux is applied to an intermediate region between the pair of lands of the substrate and the solder precoat so that the flux fits within a rectangular region circumscribing the pair of lands when viewed from a normal direction of the substrate; A flux application method, wherein the height position of the peak of the flux applied to the intermediate region is higher than the height position of the peak of either of the pair of solder precoats.

2. The flux application method of claim 1 , wherein the amount of the flux applied to the intermediate region is greater than the amount of the flux applied to the solder precoat.

3. 3. The flux applying method according to claim 1, wherein in the applying step, the flux is applied using a mask having a first opening corresponding to the intermediate region and a pair of second openings corresponding to the solder precoat.

4. The flux applying method according to claim 3 , wherein an opening area of ​​the first opening is larger than an opening area of ​​each of the pair of second openings.

5. 3. The flux applying method according to claim 1, wherein in the applying step, the flux is applied using a mask having openings commonly corresponding to both the intermediate region and the solder precoat.

6. a preparation step of preparing a substrate having a pair of lands each having a solder precoat formed thereon; a coating step of coating at least the solder precoat with flux; a mounting step of mounting an electronic component on the solder precoat to which the flux has been applied; a reflow process of soldering the electronic component to the pair of lands by heating the substrate; Equipped with In the application step, the flux is applied to an intermediate region between the pair of lands of the substrate and the solder precoat so that the flux fits within a rectangular region circumscribing the pair of lands when viewed from a normal direction of the substrate; a height position of the peak of the flux applied to the intermediate region being higher than a height position of the peak of either of the pair of solder precoats;

7. 7. The method for manufacturing a mounting board according to claim 6, wherein the amount of the flux applied to the intermediate region is greater than the amount of the flux applied to the solder precoat.

8. 8. The mounting substrate manufacturing method according to claim 6, wherein in the applying step, the flux is applied using a mask having a first opening corresponding to the intermediate region and a pair of second openings corresponding to the solder precoat.

9. The method for manufacturing a mounting substrate according to claim 8 , wherein an opening area of ​​the first opening is larger than an opening area of ​​each of the pair of second openings.

10. 8. The method for manufacturing a mounting substrate according to claim 6, wherein in the applying step, the flux is applied using a mask having an opening commonly corresponding to both the intermediate region and the solder precoat.

Images